I followed the implied installation instructions, in install.xml:
Set permission chmod 777 to directory sitemap.
As a check, I looked in all the directories and physically inventoried the required files, above.
So, they all exist.
As per instructions, I removed: install_sitemap_fx.php.
Yet, my ACP still does not show a link for sitemap fx.
Further, when I go to: http://www.nnnnn.com/phpbb3/sitemap.php
This XML file does not appear to have any style information associated with it. The document tree is shown below.
Yet, when I examine the sitemap directory, I see that it has been filling up with .xml files and that they are of varying sizes.
I think it's time to throw in the towel, on this one!
I feel as though I'm just spinning my wheels and wasting time.
I've been working on this mod for weeks, now, - far longer than this mod should have taken - and it's still not performing as advertised.
Further, the installation instructions are vague and there doesn't appear to be any support, for this mod.